1. Field of the Invention
The present invention relates in general to the control of the display of a caption in video signal processing systems, and more particularly to an apparatus and a method for controlling the display of a caption, in which the position in which a caption is to be displayed can be moved freely on a screen, a visible range of a video signal on a screen can be maximized and caption position information set by the user can be stored.
1. Description of the Prior Art
In conventional video signal processing systems, a caption process is performed by decoding character code data placed on the 21st line of an odd field of a video signal and displaying the decoded data on a particular position of a screen of a monitor of a television or a video cassette recorder (VCR). In the case Where a video tape made in one country is to be distributed in the other country, the rows of speech on the video tape in the language of one country may be translated into that of the other country and the translated rows are then dubbed onto the video tape to be displayed as a caption on the screen of the monitor, for the purpose of facilitating a viewer's understanding. For example, the rows of a video tape made in English may be caption-processed in Hangul.
In the conventional video tape, the rows of which are directly dubbed in Hangul as mentioned above, the viewer cannot select the position of the display of the dubbed caption at his option. This form of caption is commonly referred to as a so-called "open" caption.
On the other hand, the original English rows encoded on the 21st line of the odd field of the video signal can be decoded and then displayed as a caption on the screen of the monitor according to a viewer's selection. This form of caption is commonly referred to as a so-called "closed" caption. In this case, the caption process is performed by displaying the rows encoded on the 21st line of the odd field of the video signal in a specified position of the screen. Generally, the caption is displayed within the range of 4 rows on the screen which is divided into 15 equal rows.
Referring to FIG. 1, there is shown a block diagram of a conventional apparatus for controlling the caption display. As shown in this drawing, the conventional caption display control apparatus comprises a remote controller 1 for generating a plurality of mode signals to perform modes corresponding to various keys in a video signal processing system and remotely transmitting the generated mode signals, a remote control signal receiver 2 for receiving the mode signals transmitted remotely from the remote controller 1, and a microprocessor 3 for outputting a plurality of control signals to perform the modes corresponding to the mode signals received by the remote control signal receiver 2.
A caption processing circuit 4 is operated under the control of the microprocessor 3 to extract a caption signal from a video signal, decode the extracted caption signal and display character codes of the decoded caption signal as a caption at a position on a screen which is indicated by control codes of the decoded caption signal.
A monitor 5 is provided in the conventional caption display control apparatus to display the caption from the caption processing circuit 4 on the screen thereof.
The caption processing circuit 4 includes a caption signal extractor 11 for extracting the caption signal from the video signal. Here, the caption signal is placed on a particular row of the video signal.
The caption processing circuit 4 also includes a decoder 12 for decoding the extracted caption signal from the caption signal extractor 11 to extract the control codes and the character codes from the caption signal. The control code contains preselected position information, attribute information and indent information necessary to the display of the caption. The preselected position information indicates the position of the caption to be displayed and the attribute information indicates a form of the caption to be displayed. The character code is actually displayed as the caption.
Also, the caption processing circuit 4 includes an on-screen display unit 13 for displaying the character code from the decoder 12 as the caption on the screen of the monitor 5 in accordance with the control code from the decoder 12.
The operation of the conventional caption display control apparatus with the above-mentioned construction will hereinafter be described with reference to FIGS. 1 to 3E.
First, when a caption select key on the remote controller 1 is pushed by the user, the remote controller 1 outputs remotely a mode signal corresponding to the pushed caption select key to the remote control signal receiver 2. As a result, the remote control signal receiver 2 receives the corresponding mode signal from the remote controller 1.
The mode signal received by the remote control signal receiver 2 is applied to the microprocessor 3. In response to the mode signal from the remote control signal receiver 2, the microprocessor 3 outputs a control signal corresponding to the received mode signal to perform the corresponding mode of operation. The control signal from the microprocessor 3 is applied to the caption processing circuit 4.
In the caption processing circuit 4, the caption signal extractor 11 extracts the caption signal placed on a 21st line of an odd field of the video signal in response to the control signal from the microprocessor 3. The caption signal extracted by the caption signal extractor 11 is decoded by the decoder 12 for extraction of the control code and the character code from the caption signal. As mentioned above, the control code contains the preselected position information, the attribute information and the indent information necessary to the display of the caption. The preselected position information indicates the position of the caption to be displayed and the attribute information indicates the form of the caption to be displayed. The character code is actually displayed as the caption. Also, the decoder 12 outputs a control signal such that the character code is displayed in accordance with the control code. The control signal from the decoder 12 is applied to the on-screen display unit 13.
In response to the control signal from the decoder 12, the on-screen display unit 13 processes the character code to be displayed on the screen of the monitor 5. The processed character code is displayed on the screen of the monitor 5 as shown in FIG. 2A.
Generally, the caption is displayed within the 12th to 15th rows, L12-L15, of the 15 rows, L1-L15, of the screen, as shown in FIG. 2A or within first to fourth rows, L1-L4, thereof as shown in FIG. 2B. For example, in the case where the rows of the character code to be displayed are two in number, the caption is displayed in the 14th and 15th rows, L14 and L15, rather than the 12th and 13th rows, L12 and L13, as shown in FIG. 2A or in the first and second rows L1 and L2, rather than the third and fourth rows, L3 and L4, as shown in FIG. 2B. In this case, the caption is displayed in a white or blue color in a background which is boxed in a black or blue color. The remainder of the screen is processed such that the original video signal can be viewed.
However, when the caption is displayed in the 12th to 15th rows, L12-L15, of the screen as shown in FIG. 2A, it is displayed by superimposing it over the dubbed caption in the viewer's native language as stated previously, resulting in a difficulty in discrimination between the two captions.
On the other hand, when a caption move select key on the remote controller 1 is pushed by the user to freely select a position of the caption to be displayed, the remote controller 1 outputs remotely a mode signal corresponding to the pushed caption move select key to the remote control signal receiver 2. As a result, the remote control signal receiver 2 receives the corresponding mode signal from the remote controller 1.
The mode signal received by the remote control signal receiver 2 is applied to the microprocessor 3. In response to the mode signal from the remote control signal receiver 2, the microprocessor 3 outputs a control signal corresponding to the received mode signal to perform the corresponding mode. The control signal from the microprocessor 3 is applied to the caption processing circuit 4. In response to the control signal from the microprocessor 3, the caption processing circuit 4 moves the position of the caption being presently displayed on the screen as shown in FIGS. 3A to 3E.
FIG. 3A illustrates a state in which the video signal is usually displayed on the screen, FIG. 3B illustrates a state in which only the caption is boxed on the screen, FIG. 3C illustrates a state in which the whole of the rows in which the caption is displayed is boxed on the screen, FIG. 3D illustrates a state in which the caption in FIG. 3C is expanded on the screen, and FIG. 3E illustrates a state in which the caption is displayed on the whole of the screen.
With the caption move select key pushed, the caption displayed in the 12th to 15th rows of the screen is moved to the first to fourth rows thereof. In this case, if the caption is a sentence of two rows, it is displayed in the third and fourth rows of the screen, whereas the first and second rows remain empty. The empty space results in a reduction in the visible range of the video signal on the screen. Also, information regarding the moved position of the caption cannot be stored. For this reason, the position of the caption to be displayed must be set whenever the video signal processing system such as the television or the VCR is operated.